The present invention relates to an antenna, and particularly to an inverted-F dipole antenna mounted in an electronic device and operating in the ISM (Industry, Science, Medicine) frequency band for communicating with various electronic devices.
FIG. 7 illustrates a conventional planar inverted-F antenna (PIFA). The PIFA 10 includes a ground plane 12, an LPxc3x97WP rectangular radiating patch 14 and a short-circuit plate 16 having a width d1 which is narrower than the width Wp of the radiating patch 14. The short-circuit plate 16 shorts the radiating patch 14 to the ground plane 12 along a null of the TM100 dominant mode electric field of the radiating patch 14. The PIFA 10 may thus be considered a rectangular microstrip antenna in which the length of the rectangular radiating patch 14 is reduced by half by the connection of the short-circuit plate 16 at the TM100 dominant mode null. The short-circuit plate 16 supports the radiating patch 14 at a distance d2 above the ground plane 12. The radiating patch 14 is fed by a TEM transmission line 18 from the back of the ground plane 12, at a point located a distance d3 from the short-circuit plate 16. The transmission line 18 has a width d4 and includes an inner conductor 20 surrounded by an outer conductor 22. The PIFA 10 is suited for use in personal base stations, handsets and other wireless communication terminals because it has a large bandwidth and can be implemented using an air dielectric as shown in FIG. 7.
However, in this design, the inner conductor 20 of the TEM transmission line 18 penetrates through the ground plane 12 and connects with the radiating patch 14 and the outer conductor 22 connects with the ground plane 12. This design makes the assembly more complicated and increases the cost of the antenna. Furthermore, the antenna occupies a large space, so it goes against the trend toward miniaturization of electronic devices.
The present invention is directed to solving the above problems and satisfying the need for a simple antenna of the character described.
A primary object, therefore, of the present invention is to provide an improved antenna which occupies a small space and has a simplified manufacture.
In order to achieve the objects set forth, an inverted-F dipole antenna in accordance with the present invention comprises an antenna body, an antenna base, a connector providing an electrical interface to an RF circuitry and a cable connecting the antenna body with the connector. The antenna body includes two metal arms and a bended wire connecting the two arms. The antenna base includes a rectangular insulative board and a metal sheet attached to one surface of the board. The antenna body is mounted on the antenna base with the bended wire thereof being attached to a second surface of the board opposite to the metal sheet. The cable serves as a RF feeder and one of the metal arms serves as a radiation device.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.